I can't agree with that. eCharts is good, but https://plotly.com/javascript/ is also super nice and I am actively following https://observablehq.com/plot/ which seems on a path to true greatness.

Plotly is full of undocumented features. My guess is because they have an entire consulting business helping devs with this

plotly... please... I hope I never have to touch that again, the documentation is so bad. It's not on the same level as eCharts.